- the lenses from the APS-C format could be reused without any loss.The image covers all the sensor area whereas this is not true for the Sony FF.

- I would propose 2 adapters: a usual adapter, which would have the advantage to use the lens at a different equivalent focal. The 55-200 will become a 75-270, which is better for wildlife photography. The 23mmf1.4 could be used for portrait. Plus a speed booster adapter for those who want a fast lens.

- Compatible with panasonic/Olympus lens.

- I personally believe that FF is overrated. This is better, I admit but the difference is going to decrease more and more. And FF does not perform better in low light, I am happy with f1.4, I have no need to go wider (or just for 1℅ of my pictures)

- I would have 2 bodies, a more pocketable m43 and the APS-C.

- by going FF, they would just be followers.

m43 start to have stunning IQ. Even smaller sensor with RX10 is impressive...

Going to the opposite way (compared to Sony) would not be stupid. Think about the Sony Nex owners who will have to buy new lenses if they want to switch !!! Whereas m43 offers a second use for our lenses !!!